Is this abuse or just frustration?

I’m going to keep it as short as possible. My boyfriend and father of my two kids has been “off”. Our kids are only a year apart which I just had one of them recently. So I have a toddler and baby. He’s an amazing father to them. He loves them more than anything. Only problem is if they start to throw a fit/tantrum or just being a baby!? He gets aggressive. He’s yelled at our one month old and has told him to stop the crying once he doesn’t stop. I started to be around at these times and noticed how aggressive he is to both kids when they are upset. He shoves the binky in their mouths and hold it with force while they are going crazy, he’s physically forcefully picked up our youngest and thrown him over his shoulder to burp him but in a forceful way almost shaking him. Today, I saw him do it multiple times in front of me where I told him he needs to relax and calm down. He told me everything’s fine. I told him he’s being rough and he just told me it’s fine. He’s fine. Now I’m paranoid every time I hear the babies crying… he has started to get physical when we have fought. He’s forcefully grabbed my phone out of my hands. He’s grabbed my keys from my hands so hard that I got an injured finger. Is this the start of abuse? When the kids and everyone is good he’s good. But once tantrums start he turns into something evil…